Bad formatting for Libraries header

[garyrob]

In the Quickstart, there's a substantial section called "Libraries". It seems to be as important as the other sections such as "EXPANDING OUR DUMMY APPLICATION", "USING GIT", etc.

But the way it appears topographically is in a smaller type size which makes it look like a subsection of the second "OPAM SWITCH" heading. I discussed that heading in another issue; I believe it shouldn't be there at all and is a mistake due to the text being garbled in an editing process. And I believe the "Libraries" subsection should be its own "LIBRARIES" section, equal to the other main sections.

[bluddy]

Feel free to offer a fix.

[garyrob]

I created PR 179 to address this.